1. Technical Field
The present invention relates to a driver program or the like for causing a host apparatus to execute a processing of generating image data in the host apparatus and transferring those image data to a printing apparatus, and more particularly to a driver program or the like that makes it possible to reduce the volume of image data to be stored in the host apparatus and to conduct data transfer without a delay in a printing completion time.
2. Background Art
Usually in a printing system for executing printing on a printing medium such as paper, printing data is transmitted from a host apparatus, such as a personal computer, and the printing apparatus that received printing data implements printing based on the printing data. Before the printing is completed, the following types of processing are carried out with respect to the printing data: a processing of obtaining image data in which the data of a printing request issued from an application of the host apparatus are represented as color density values for each pixel, a processing of converting the color representation of the image data into color representation in the printing apparatus, and a processing of representing the color converted data as dot images.
In recent years, the so-called host base processing in which all the operations prior to color conversion processing are implemented in the host apparatus has been conducted. In such cases, the image data after color conversion are compressed in the host apparatus and then transmitted to the printing apparatus. In the printing apparatus, the received data are used after decompression. Furthermore, in the compression processing of the image data transmitted from the host apparatus, the processing is usually conducted for each of the regions (called bands) that are obtained by dividing the range of one plane of the printing medium to prescribed lengths in the height direction. For example, when image data after color conversion are represented by Y (yellow), M (magenta), C (cyan), and K (black), the image data comprising data of those four colors are sequentially compressed in band units and become a state suitable for transmission to the printing apparatus.
Several methods have been used in the past for transferring the data subjected to such compression processing to the printing apparatus. With one of such methods the transmission to the printing apparatus is sequentially conducted from the image data of the compressed bands, following the sequence of the above-described compression processing. The process of transmitting the image data comprising data of all the colors for each band will be referred to hereinbelow as “data transfer in a band sequence”. When the printing apparatus is, for example, an apparatus for conducting printing in one-plane units of the printing medium, such as a four-cycle laser printer, the printing apparatus cannot start printing processing unless at least the image data of one color of one plane are received. Therefore, when data transfer is conducted in a band sequence, the printing apparatus does not start printing processing till the image data of all the colors of one plane are received.
Further, with another transfer method for data, the image data compressed for each band are stored for one plane in the host apparatus and then the stored image data for one plane are transmitted sequentially color by color. For example, when the image data are composed of data of four colors YMCK, first, all the data for Y, of the image data of one plane that were stored, are transmitted, and then all the data for M, all the data for C, and all the data for K are sequentially transferred. The process in which the image data of one plane are thus transmitted color by color in turn will be referred to hereinbelow as “data transfer in a plane sequence”. This method is employed, for example, in the apparatus described in Japanese Patent Application Laid-open No. 2002-236563. When the printing apparatus is a four-cycle laser printer or the like and carries out the printing processing color by color for each plane, the printing processing can be started even if all the image data for one plane have not been assembled. Conducting such data transfer in a plane sequence makes it unnecessary to delay the start of printing processing till the image data of all the colors of one plane are received. The so-called flying start is possible.